<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    div{
        width: 100px;
        height: 100px;
    }
    .box{
        display: flex;
    }
    .son{
        background-color: aqua;
    }
    .son2{
        background-color: red;
    }
</style>
<body>
    <div class="box">
        <div class="son">1</div>
        <div class="son2">2</div>
    </div>
</body>

</html>